Spire proposes to fabricate HgCdTe, front-side illuminated, electrically selectable, two-color infrared detector arrays for high resolution biomedical thermography. The proposed device is a two terminal, n-p-n heterostructure which can be thought of as two back-to-back diodes. Through proper selection of the material composition and application of an appropriate bias, the device can be made sensitive to two different spectral bands and would be used in biomedical thermal imaging applications where temperature discrimination is important. With good junction characteristics, background-limited performance (BLIP) should be achievable in both bands. In addition, the device requires only two terminals, thus permitting a mosaic of detectors to be hybridized with a silicon signal processor using existing bump hybridization technology. The devices will be fabricated in a 4 x 4 configuration. Temperature resolution of 0.01 degrees C should be achievable with these devices. CdTe will serve as the passivant, and a gate will be used to control the surface potential. In Phase 1, Spire will design, fabricate and test the proposed two-color HgCdTe IR detector array in a 4 x 4 configuration. MetalOrganic Chemical Vapor Deposition (MOCVD) materials technology will be used and a gate will be employed to control surface leakage. The devices will be characterized for spectral detectivity, responsivity, spectral response, and noise performance. Phase H will optimize the device design and the MOCVD deposition parameters for optimal spectral detectivity and maximum efficiency. Phase II will also address the fabrication of these two-color detectors on alternate substrates (GaAs/Si).